Medical device for stimulation of the HIS bundle

ABSTRACT

An implantable medical system for delivering pacing pulses to HIS bundle of a heart of a patient when implanted in said patient includes a medical lead, which is adapted to be attached with a distal end to tissue of said heart, including a at least two electrodes arranged being electrically separated from each other. The implantable medical device connectable to the medical lead includes a pacing circuit adapted to deliver the pacing pulses to said heart via the medical lead, a selection device connected between the pacing circuit and the electrodes adapted to selectively activate at least one of said electrodes, and a processing device adapted to control the selection device to selectively activate at least one of the electrodes to direct the pacing pulses to the HIS bundle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an implantable medical systemincluding an implantable medical device and an implantable medical leadfor pacing the HIS Bundle.

2. Description of the Prior Art

Many studies have recently demonstrated the potential detrimentaleffects of RV (Right Ventricular) apex pacing. The stimulation of theventricles through RV apex generates an activation pattern similar toLBBB (Left Bundle Branch Block) patients, with unsynchronized right andleft ventricles as a result. The long term effects of RV apical pacingare thought to be (in the worst case) advancing CHF (Cardiac HeartFailure) or compromised hemodynamics.

One way to overcome these disadvantages is to implant a CRT (CardiacRhythm Therapy) system with a LV (Left Ventricular) that can restore thesynchronization between the left ventricle and the right ventricle.However, for those patients which have an intact conduction system belowthe AV-node, pacing in upper regions in the RVOT/RV septal wall—or morebeneficial—the Bundle of HIS, may restore synchronization as well.

Pacing in HIS Bundle may actually generate EGM's being more or lessidentical with the intrinsic or native ones. The pacing signal ispropagated along the Purkinje fiber system and the patient will benefitfrom having a true physiologic pacing. However, pacing of the HIS Bundlearea is difficult to achieve and/or optimize. It is a small area locateddeep in the tissue between the RA (Right Atrium) and RV, near themembranous septum or the interventricular septum. In addition, the depthat which the intrinsic conduction system lies is individual to everyperson.

Due to the fact that the Bundle of HIS is a structure located deepwithin the myocardium, the positioning of the medical lead must beoptimized in three dimensions. Typically, the Bundle of HIS is reachedfrom the atrium by mapping in the area of the Triangle of Koch. Thecorrect region at which the endocardium should be penetrated with thelead in order to reach the Bundle of HIS is identified by finding thespot where the largest HIS Bundle potential is measured. The lead helixis then fixated in this spot.

However, studies have revealed that both the capture threshold and thesense thresholds as well as the ability to distinguish the signal fromthe HIS Bundle with the implantable lead is to a high degree dependenton the depth of the electrode (i.e. the helix) in the tissue, see, forexample, Deshmukh et al., Circulation 2000; 101; 869-877 and Laske etal., PACE 2006; 29; 397-405. With a conventional lead, which has alength of the helix of approximately 1.5-2.0 mm, the helix may in somecases never reach the optimal site. In order to reach the desired spotin close proximity to the bundle of HIS, a longer helix will berequired. This has been studied in Karpawich et al., PACE, Part II,1992; 15; 2011-2015, where a helix having a length of 4.5 mm was used topace HIS Bundle. A long conductive helix is however associated withnegative side effects. For example, the depolarization of the tissue maybecome indistinctive relative the Bundle of HIS and a large conductivesurface area of the helix will entail a reduced impedance.

In U.S. Pat. No. 7,177,704, a medical lead including a helix for pacingHIS Bundle is shown. The helically shaped electrode is partially maskedwith an insulative material, leaving an intermediate area unmasked andelectrically conductive to allow for pacing at specific depths withinthe heart tissue. During the implantation, the physician rotates theelectrode in and out of the tissue to determine an optimal position inwhich to pace the portion of the intrinsic conductive system. Since thedepth at which the intrinsic system lies is different for every person,the physician rotates the helical electrode in and out of the tissue todetermine an optimal conductive position. Consequently, the implantationprocedure of the medical lead according to U.S. Pat. No. 7,177,704 maybe cumbersome and time-consuming.

Thus, there is still a need within the art for an improved implantablemedical device and an implantable medical lead capable of providing areliable and accurate pacing of the His Bundle. There is also a needwithin the art of an improved implantable medical device and animplantable medical lead for stimulation of the His Bundle that can beimplanted in an efficient way.

SUMMARY OF THE INVENTION

Thus, an object of the present invention is to provide an improvedmedical system, implantable medical device and medical lead capable ofstimulating the heart of a patient such that a substantially native-likeresponse can be achieved.

Another object of the present invention is to provide an improvedmedical system, implantable medical device and medical lead capable ofdelivering a reliable and accurate pacing of His Bundle.

A further object of the present invention is to provide an improvedmedical system, implantable medical device and medical lead forstimulation of His Bundle that can be implanted in a swift and efficientway.

Yet another object of the present invention is to provide an improvedmedical system, implantable medical device and medical lead forstimulation of His Bundle that enables an efficient post-implantoptimization of the stimulation electrode position without the need ofintervention.

According to an aspect of the present invention, there is provided amedical system for delivering pacing pulses to the HIS bundle of a heartof a patient when implanted in the patient or during an implantationprocedure. The system includes at least one medical lead, which isadapted to be attached with a distal end to tissue of the heart, themedical lead including a lead body including a flexible insulatingtubing and at least one conductor arranged within the tubing, apenetrating electrode arrangement in the distal end for enablingattachment of the lead to tissue, and at least two electrodes arrangedon the electrode arrangement being electrically separated from eachother, each being connected to the at least one conductor. The systemalso has a selection device connected to the electrodes and beingadapted to selectively activate at least one of the electrodes.Furthermore, the system has an implantable medical device connectable tothe medical lead, the medical device having a pacing circuit adapted todeliver the pacing pulses to the heart via the selection device, themedical lead and the at least one activated electrodes.

According to a second aspect of the present invention, there is provideda method for delivering pacing pulses to the HIS bundle of a heart of apatient. The method includes delivering pacing pulses to the heart via amedical lead adapted to be attached with a distal end to tissue of theheart, wherein the medical lead has a lead body including a flexibleinsulating tubing and at least one conductor arranged within the tubing,a penetrating electrode arrangement in the distal end for enablingattachment of the lead to tissue, and at least two electrodes arrangedon the electrode arrangement being electrically separated from eachother, each being connected to the at least one conductor.

According to another aspect of the present invention, there is provideda medical lead connectable to a medical system for delivering pacingpulses to the HIS bundle of a heart of a patient when implanted in thepatient or during an implantation procedure of the lead from animplantable medical device of the medical system. The medical leadincludes a lead body including a flexible insulating tubing and at leastone conductor arranged within the tubing, a penetrating electrodearrangement in the distal end for enabling attachment of the lead totissue, at least two electrodes arranged on the electrode arrangementbeing electrically separated from each other, each being connected tothe at least one conductor, wherein the at least one electrode can beselectively activated to direct the pacing pulses to the HIS bundle.

According to a further aspect of the present invention, there isprovided an implantable medical device for delivering pacing pulses tothe HIS bundle of a heart of a patient when implanted in the patient orduring an implantation procedure of the device, which device isconnectable to a medical lead being adapted to be attached with a distalend to tissue of the heart, which medical lead includes a lead bodyincluding a flexible insulating tubing and at least one conductorarranged within the tubing, a penetrating electrode arrangement in thedistal end for enabling attachment of the lead to tissue, at least twoelectrodes arranged on the electrode arrangement being electricallyseparated from each other, each being connected to the at least oneconductor. Furthermore, the implantable medical device has a pacingcircuit adapted to deliver the pacing pulses to the heart via themedical lead.

The present invention, in contrast to ventricular pacing, is based onpacing or stimulation at the HIS bundle, for example, low in atrialseptum or high in the interventricular septum being similar to naturalor intrinsic stimulation since depolarization in that case comes via thePurkinje system and subsequently spreads rapidly across the ventriclewith more efficient heartbeats as a result. In Circulation, Journal ofthe American Heart Association, 1970; 41; 77-87, it is, for example,shown that during pacing at the HIS bundle, the QRS complex is identicalto that during normal sinus rhythm. This is due to that induced (orspontaneous) pulses arising from HIS bundle are normally transmittedthrough the same pathways to the ventricular musculature producingsimilar patterns of ventricular depolarization. On the other hand,direct stimulation of the ventricular musculature or the right bundlebranch produces aberrant QRS complex due to alteration in ventricularactivation pattern from that during normal sinus rhythm. In order tomake use of these findings the present invention is based on the idea ofproviding a medical lead with a penetrating electrode arrangement in thedistal end including a number of electrodes located at differentpositions that can be selectively activated to stimulate tissue atdifferent depths and locations. Thereby, the implantation procedure canbe improved and can be made more swift and efficient with regard to, forexample, time-consumption in comparison to the normal procedure due tothe fact that the electrode can be attached to tissue (penetrate theendocardium) and that the physician thereafter may select the electrodeproviding the best HIS bundle stimulation. Moreover, the lead may alsobe used to adapt for morphological changes in the patient, for example,during a follow-up at the physician and an optimization (a selection ofwhich electrode to be used for stimulation) can be performed to adaptfor specific circumstances, for example, evolvement of fibrous capsulearound the lead tip or lead migration/maturation. For example, theimplantable medical device can be reconfigured to utilize anotherelectrode more distal or more proximal to the first one. The system ormedical device may also be adapted to automatically adapt formorphological changes in the patient and an optimization (a selection ofwhich electrode to be used for stimulation) can be performed to adaptfor specific circumstances, for example, evolvement of fibrous capsulearound the lead tip or lead migration/maturation.

In one embodiment of the present invention, the medical device includesa processing device adapted to control the selection device toselectively activate at least one of the electrodes to direct the pacingpulses to HIS bundle. The processing device thus controls the selectiondevice to selectively activate one or more electrode, which can beperformed to optimize the stimulation at implantation, eitherautomatically or upon instruction from the physician e.g. via anexternal programmer device, at regular intervals or continuously duringoperation of the implantable medical device to adapt for morphologicalchanges in the patient or, for example, during a follow-up at thephysician and an optimization (a selection of which electrode to be usedfor stimulation) can be performed to adapt for specific circumstances,for example, evolvement of fibrous capsule around the lead tip or leadmigration/maturation using, for example, surface ECG signals. Hence, theelectrode usage can be adjusted if inferior pacing characteristics uponlead migration or micro dislodgement appear when implanted, for example,in a chronic setting. For example, the implantable medical device can bereconfigured to utilize another electrode more distal or more proximalto the first one.

According to another embodiment, the selection device can be controlledmanually. Thereby, a physician may, for example, during a follow up orduring an implantation control the selection device to selectivelyactivate one or more electrode.

In one embodiment, the medical system includes an extracorporealprogrammer device adapted to control the selection device or theprocessing circuit to selectively activate one or more electrode. Aphysician may, in turn, provide the programmer device with instructionsor the programmer device may automatically control the selection deviceto selectively activate one or more electrode. The programmer device maycommunicate with the implantable medical device wirelessly or via aphysical connection.

In embodiments of the present invention, the programmer device furtherhas a processing device adapted to control the selection device toselectively activate at least one of the electrodes to direct the pacingpulses to HIS bundle, the processing device is adapted to control theselection device to selectively activate at least one of the electrodesby connecting the at least one electrode with the pacing circuit basedon at least one selection parameter.

In an embodiment of the present invention, the programmer device isadapted to obtain ECG or IEGM signals corresponding to a physiologicalactivity of the heart and/or measurement signals corresponding to theoperation of the electrodes. The IEGM signals corresponding to aphysiological activity of the heart and/or measurement signalscorresponding to the operation of the electrodes can be obtained from ameasurement circuit of the medical device.

Thereby, the different electrodes of the medical lead can be evaluatedbased on physiological or hemodynamic activity of the heart and/or thefunctioning or operation of the electrodes. For example, the evaluationcan be based on ECG or IEGM signals, a pace-ventricular interval, asense-ventricular interval, capture thresholds and/or sense thresholds.During an implantation, the evaluation results or evaluation measurescan be displayed on an external programmer device thereby allowing aphysician performing the implantation to continuously monitor theevaluation results. The results can be transferred wirelessly or via aphysical connection to the programmer device from the implantablemedical device or the medical lead. Furthermore, when implanted, themeasurement circuit may continuously or at regular intervals determineevaluation results. These results can be used to optimize the electrodelocation, i.e. change stimulation electrode, after implantation. Theresults may also be transferred to an external programmer device,whereby a physician may be informed that a post-implant optimizationshould be performed or has been performed.

In an embodiment of the present invention, the processing device isadapted to determine the at least one selection parameter based on anevaluation of the obtained IEGM signals and/or the measurement signals,which thus may be used for an optimization as described above.

In accordance with a further embodiment of the present invention, theelectrodes, during a test procedure, are activated according to apredetermined scheme, the selection parameter(-s) obtained during apacing period for each respective electrode is(are) evaluated todetermine which electrode to use for the HIS bundle pacing, and theselection circuit is instructed to activate the determined electrode forHIS bundle pacing. This test procedure can be automatically performed atregular intervals or upon receiving an instruction from, for example, aphysician via an external programmer device to adapt, for example,morphological changes in the patient or if inferior pacingcharacteristics upon lead migration or micro dislodgement appear whenimplanted, i.e. in the chronic setting. By automatically performing thetest procedure at regular intervals, morphological changes in thepatient or inferior pacing characteristics upon lead migration or microdislodgement can be detected and compensated for at an early stage.

According to a further embodiment of the present invention, a conductiontime from sensing a native event at the bundle of HIS or from a deliveryof at least one pacing pulse to the HIS bundle to the subsequentventricular activation is determined using surface ECG signals or IEGMsignals and/or measurement signals corresponding to the operation of theelectrodes. The selection circuit is instructed to initiate the testprocedure if the determined conduction time exceeds a predeterminedreference threshold. The reference threshold may be a recorded referenceconduction time for the patient corresponding to the period of time fromsensing a native event at the bundle of HIS or from a delivery of atleast one pacing pulse to the HIS bundle to the subsequent ventricularactivation can be determined.

In another alternative embodiment of the present invention, a morphologyof the QRS complex, including the amplitude, and/or configuration,and/or duration, is determined for respective consecutive cardiac eventsusing the measurement sensing signals corresponding to the physiologicalactivity, the determined QRS complex is evaluated to determine whetherit satisfies predetermined conditions, for example a predeterminedreference QRS complex, and the selection circuit is instructed toinitiate the test procedure if the determined QRS complex do notsatisfies the predetermined conditions. The predetermined conditions maybe a recorded reference QRS complex for the patient. The morphologies ofthe reference QRS complex may be compared to the measured QRS complexand if any substantial deviation is detected, for example, in amplitudeof the R-wave, duration of the QRS complex, and/or configuration of thecomplex.

In alternatives of the present invention, the selection device isarranged in a medical lead or in the implantable medical device.

In one embodiment of medical lead the penetrating electrode arrangementincludes a rotatable helix adapted for enabling an attachment of thelead to tissue by screwing the helix into the tissue, the helixcomprising the at least two electrodes. In another embodiment of themedical lead the penetrating electrode arrangement includes a rotatablehelix adapted for enabling an attachment of the lead to tissue byscrewing the helix into the tissue and an penetrating pin comprising theat least two electrodes, the penetrating pin being arranged such thatthe helix partly encircles the pin.

As will be apparent to those of skill in the art, steps of the methodsaccording to the present invention, as well as preferred embodimentsthereof, are suitable to realize as computer program or as a computerreadable medium.

Further objects and advantages of the present invention will bediscussed below by means of exemplifying embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified partly cutaway view illustrating an implantablestimulator including an electrode configuration according to the presentinvention.

FIG. 2 illustrates simultaneous recordings of bipolar electrogram fromthe area of A-V junction and a standard ECG lead at normal sinus rhythm,atrial pacing an pacing at HIS bundle at different rates, respectively.

FIG. 3 is an illustration in block diagram form of a system according toan embodiment of the present invention including an implantablestimulator.

FIG. 4 is a schematic view of an penetrating electrode arrangementaccording to an embodiment of the present invention.

FIG. 5 is a schematic view of an penetrating electrode arrangementaccording to another embodiment of the present invention.

FIG. 6 is an illustration in block diagram form of a system according toanother embodiment of the present invention including an implantablestimulator.

FIG. 7 is an illustration in block diagram form of a system according toa further embodiment of the present invention including an implantablestimulator.

FIG. 8 is a schematic flow chart illustrating the principles of themethod according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a description of exemplifying embodiments in accordancewith the present invention. This description is not to be taken inlimiting sense, but is made merely for the purposes of describing thegeneral principles of the invention.

In FIG. 1 an arrangement of a implantable pacing system 10 according toan embodiment of the present invention implanted in a patient (notshown), the pacing system 10 includes a subcutaneously disposedstimulation device or pacemaker 12. The stimulation device 12 is inelectrical communication with a patient's heart 1 by way of two leads 20and 30 suitable for delivering stimulation, which leads 20 and 30 areconnectable to the stimulation device 12. The illustrated portions ofthe heart 1 include right atrium RA, the right ventricle RV, the leftatrium LA, the left ventricle LV, cardiac walls 2, the ventricle septum4, the valve plane 6, and the apex 8.

In order to provide stimulation therapy to the right atrium RA, thestimulation device 12 is coupled to an implantable right atrial lead 20having at least one electrode 24, e.g. a tip electrode, adapted toplaced or located in contact with the atrial wall. The electrode 24 isarranged for sensing electrical activity, intrinsic or evoked, in theright atrium RA.

In order to provide pacing to HIS bundle, the stimulation device 12 iscoupled to a lead 30 designed to penetrate the endocardium from rightatrium RA, so as to place at least one electrode (not shown) in contactwith the HIS bundle. The lead 30 and the at least one electrode forstimulating the HIS bundle will be described in more detail below withreference to FIGS. 3 and 4. The HIS bundle electrode is capable ofsensing HIS events as well as right ventricular events, such as aventricular activation, since the period of time between a native HISevent or a paced HIS event to the subsequent ventricle contraction(activation) typically is about 70 msec.

The Bundle of HIS is reached from the atrium by mapping in the area ofthe Triangle of Koch. The correct region at which the endocardium shouldbe penetrated with the lead in order to reach the Bundle of HIS isidentified by finding the spot where the largest HIS Bundle potential ismeasured. The electrode arrangement, e.g. the lead helix, may then befixated in this spot.

A physician implanting the medical system according to the presentinvention, may begin with implanting the lead 30 into the right atrium.The physician will then look for characteristics close to the AV node inorder to locate a site where to place the electrode arrangement in theright atrium, which arrangement in this case is a rotable helix adaptedto penetrate the myocardium. For example, by using a fluoroscope, thephysician may look for the boundaries of the triangle of Koch, whichcontain HIS bundle at its apex. Upon locating this location thephysician would implant the medical lead 30 in a location believed to belocated down the electrical path of an improperly working portion of theintrinsic conduction system, i.e. the HIS bundle in this case. Thephysician then begins to stimulate the intrinsic conduction system.During the stimulation the different electrodes of the electrodearrangement is activated, for example, according to a predeterminedscheme to determine an optimal electrode for pacing HIS bundle. Sincethe location of HIS bundle may vary in three dimensions, and whichlocation also is different for every person, the physician henceselectively activates different electrodes of the electrode arrangementto determine an optimal conduction position for the particular patient.For each electrode at least one pacing measure or selection parameter isobtained to determine the function or the efficiency of the respectiveelectrode. This or these pacing measure(-s) or selection parameters canbe determined by a processing circuit of the implantable medical devicebased on, for example, measured surface ECG signals and/or measuredstimulation responses (e.g. thresholds and/or sensing values), or by aprocessing circuit of an external programmer device connected to theimplantable medical device or the medical lead. According to oneembodiment, the surface ECG is obtained and the QRS complex and T-wavecomplex is identified in the surface ECG and when HIS bundle is reached,the QRS complex and T-wave complex should substantially correspond to anative QRS complex and a native T-wave complex with respect tomorphology, including amplitude, configuration and duration being theresult from an intrinsic event. This is described by Deshmukh et al, inCirculation 2000; 101; 869-877. According to another alternative, theperiod of time between a stimulation at the HIS bundle and thesubsequent ventricular event (HIS-ventricular interval or H-V-interval)is determined and this period of time is compared with the period oftime for a native stimulation, i.e. a spontaneous sensed event at HISand the sensed ventricular event. When the HIS bundle is reached, thetwo periods of time should be substantially equal, i.e. the length ofthe respective periods of time should substantially coincide.

With reference to FIG. 2, recordings obtained during tests performed onpatients that illustrate that pacing or stimulation at the HIS bundle,for example, low in atrial septum or high in the interventricular septumprovides similar results as natural or intrinsic stimulation will bediscussed. The waveforms referred to as 14 a-14 d shown in FIG. 2illustrate simultaneous recording of bipolar electrogram (BE) from thearea of A-V junction and a standard ECG lead (L1), respectively. BE (BH)represents bipolar electrogram from the area of the A-V junction, BE(RA) represents bipolar electrogram from the right atrium, L-Irepresents lead I of the standard lead electrogram, NSR representsnormal sinus rhythm, A pacing represents atrial pacing, BH pacingrepresents pacing at bundle of HIS, PI represents pacing impulse, andPI-R represents the time interval from the pacing impulse to the onsetof the QRS complex. The waveforms referred to as 14 a show therecordings at normal sinus rhythm of 65 per minute. As can be seen, theA-H and H-V interval are 100 and 60 msec, respectively. From thewaveform referred to as 14 b, which illustrates atrial pacing at 90 perminute, it can be seen that the A-H interval was prolonged to 140 msecwhile the H-V-interval remained unchanged at 60 msec. In waveformsreferred to as 14 c and 14 d, respectively, bundle of HIS pacing atrates of 90 and 110 per minute are shown, respectively. The pacingimpulse (PI) to the onset of the QRS complex time (PI-R) remainedconstant at 60 msec during both levels of BH pacing rates, i.e. equal tothe H-V-interval at normal sinus rhythm and at atrial pacing.Furthermore, it can also been seen that the shape or morphology of theQRS complex is similar to that during normal sinus rhythm, e.g. nosubstantial change in amplitude, configuration, and duration.

Turning now to FIG. 3, an embodiment of a implantable medical device,e.g. a stimulation device or a pacemaker according to the presentinvention will be discussed. FIG. 3 is a schematic block diagram of thestimulation device. For illustrative purposes, reference is made to FIG.1 for the elements of the leads that are intended for positioning in orat the heart.

The stimulation device 12 is connected to a heart 1 order to sense heartsignals and emit stimulation pulses to the heart 1. Electrodes locatedwithin and at the heart and outside the heart, for example, anindifferent electrode (which, in this instance, consists of theenclosure of the stimulation device 12 but can also consist of aseparate electrode located somewhere in the body) are connected to apulse generator 36 in the stimulation device 12. The electrodes locatedwithin are connected to the stimulation device 12 via leads, forexample, the leads 20 and 30 shown in FIG. 1. A measurement and detectorcircuit 38 is also connected to the electrodes in order to senseactivity of the heart.

The pulse generator 36 and the measurement circuit 38 are controlled bya control unit 40 which regulates the stimulation pulses with respect toamplitude, duration and stimulation interval, the sensitivity of themeasurement circuit 38 etc.

The lead 30 includes a penetrating electrode arrangement (which will bedescribed in more detail below with reference to FIGS. 4 and 5) in thedistal end for enabling attachment of the lead to tissue. Thepenetrating electrode arrangement includes at least two electrodeselectrically separated from each other. The electrodes can beselectively activated to deliver stimulation to a selected tissue site,i.e. the best electrode for stimulating HIS bundle can be selected. Theelectrodes are connected to the pulse generator 36 and the measurementcircuit 38 via a selection device or a switching device 42 (see FIGS. 6and 7), which will be discussed below with reference to FIGS. 4 and 5.

A control unit 40 controls the pulse generator 36, the measurementcircuit 38, and, optionally, the selection device 42 via a data bus (notshown). The selection device 42 may, in some applications of the presentinvention, be controlled manually by the physician using, for example,an external device 46, for example a extracorporeal programmer device.The programmer device 46 may communicate with the implantable medicaldevice 12 wirelessly via a telemetry unit 44 or via a physicalconnection. This may be the case, for example, during the implantationprocedure. Using the telemetry unit 44, a physician may also program thecontrol unit 40 to perform various functions via the programmer device46.

The telemetry unit 44 is also connected to the data bus. Thus, the heartstimulator 12 can communicate, via the telemetry unit 44, with externaldevices 46, for example, an extracorporeal programmer, a home monitoringdevice, or a patient worn device via a communication network, forexample, a wireless communication network including at least oneexternal radio communication network such as wireless LAN (“Local AreaNetwork”), GSM (“Global System for Mobile communications”), or UMTS(“Universal Mobile Telecommunications System”). For a givencommunication method, a multitude of standard and/or proprietarycommunication protocols may be used. For example, and withoutlimitation, wireless (e.g. radio frequency pulse coding, spread spectrumfrequency hopping, time-hopping, etc.) and other communication protocols(e.g. SMTP, FTP, TCP/IP) may be used. Other proprietary methods andprotocols may also be used. The notification may include at least thepatient identity, the occurrence of a myocardial infarction and/or thelocation of the detected infarct within the heart. The communicationunit may be adapted to communicate with the user equipment, e.g. mobilephone, a pager or a PDA (“Personal Digital Assistant”), which is adaptedto receive the notification via, for example, Bluetooth and to transmitit via the communication network further on to the medical careinstitution.

Further, a memory circuit 48 is connected to the control unit 40, whichmemory circuit 48 may include a random access memory (RAM) and/or anon-volatile memory such as a read-only memory (ROM).

Power for the stimulation device 12 is supplied by a battery 52.

With reference now to FIG. 4, one embodiment of the penetratingelectrode arrangement of the medical lead according to the presentinvention will be discussed. The lead 60 comprises a penetratingelectrode arrangement 62 in the distal end for enabling attachment ofthe lead 60 to tissue. The penetrating electrode arrangement 62 includesa helix 63 comprising a number of individual electrodes 64 a-m, orstimulating surfaces, electrically separated from each other. In thisembodiment, the electrodes 64 a-m are arranged as ring electrodes but,however, as the skilled person realizes the electrodes may be arrangedas circular segments (e.g. a half circle or a quarter of a circle)instead of ring electrodes. The electrodes 64 a-m can be selectivelyactivated, i.e. individually addressed, to deliver stimulation to aselected tissue site, i.e. the best electrode for stimulating HIS bundlecan be selected. The electrodes 64 a-m are connected to the pulsegenerator 36 and the measurement circuit 38 via a selection device or aswitching device 42, which will be described in more detail below withreference to FIG. 6, allowing each electrode 64 a-m to be individuallyaddressed. This embodiment of the electrode arrangement can be realizedby means of a helix shaped plastic wire incorporating metallicconductors (not shown) which are isolated from each other by means of,for example, by the plastic wire or by a polymeric layer on each wire orconductor. In order to provide the electrodes 64 a-m, the plasticinsulation may be grinded away such that the conductors are exposed.

Turning now to FIG. 5, another embodiment of the penetrating electrodearrangement of the medical lead according to the present invention willbe discussed. The lead 70 comprises a penetrating electrode arrangement72 in the distal end for enabling attachment of the lead 70 to tissue.The penetrating electrode arrangement 72 includes helix 73 and nail-likepin 74 arranged within the helix 73. The pin 74 includes a number ofindividual electrodes 75 a-c, or stimulating surfaces, electricallyseparated from each other. In this embodiment, the electrodes 75 a-c arearranged as ring electrodes but, however, as the skilled person realizesthe electrodes may be arranged as circular segments (e.g. a half circleor a quarter of a circle) instead of ring electrodes. The electrodes 75a-c can be selectively activated, i.e. individually addressed, todeliver stimulation to a selected tissue site, i.e. the best electrodefor stimulating HIS bundle can be selected. The electrodes 75 a-c areconnected to the pulse generator 36 and the measurement circuit 38 via aselection device or a switching device 42, which will be described inmore detail below with reference to FIG. 6, allowing each electrode 75a-c to be individually addressed. In this embodiment, the pin 74 may bea plastic wire incorporating metallic conductors (not shown) which areisolated from each other by means of, for example, by the plastic wireor by a polymeric layer on each wire or conductor. In order to providethe electrodes 75 a-c, the plastic insulation can be grinded away suchthat the conductors are exposed.

Turning now to FIGS. 6 and 7, further embodiments of the presentinvention will be discussed. As can be seen in FIG. 6, the stimulationunit or pacemaker 12 is connected to the heart 1 by the medical leads20, 30, respectively. The medical lead 30 is comprises a penetratingelectrode arrangement in the distal end for enabling attachment of thelead to tissue, for example, the penetrating electrode arrangement asdescribed above with reference to FIG. 4 or 5. As described above, thepenetrating electrode arrangement includes a number of electrodes, or anelectrode array, electrically separated from each other. The electrodescan be selectively activated to deliver stimulation to a selected tissuesite, i.e. the best electrode for stimulating the HIS bundle can beselected. The electrodes are connected to the pulse generator 36 and themeasurement circuit 38 via the selection device or a switching device42, which is arranged at or in the medical lead 30. The operation of theselection device 42 is controlled by the control unit 40. The selectiondevice 42 may, for example, be implemented as switch. A number ofconductors 43 a-43 d is connected to a respective electrode surface ofthe penetrating electrode arrangement. In FIG. 6 only four conductorsare shown, but, as the skilled person realizes, this number ofconductors may be adapted to the number of electrode surfaces of thepenetrating electrode arrangement such that each electrode surface isconnected to the selection device 42 by means of a respective conductor.

In FIG. 7, an alternative embodiment of the present invention is shownwhere the selection device 42′ is arranged in the stimulation device 12′in connection with the control unit 40 and the medical lead 30′. Anumber of conductors 43′a-d is connected to a respective electrodesurface of the penetrating electrode arrangement. In FIG. 6 only fourconductors are shown, but, as the skilled person realizes, this numberof conductors may be adapted to the number of electrode surfaces of thepenetrating electrode arrangement such that each electrode surface isconnected to the selection device 42′ by means of a respectiveconductor.

Referring now to FIG. 8, an embodiment of the method for deliveringpacing pulses to HIS bundle of a heart of a patient according to thepresent invention will be discussed. First at step S100, pacing pulsesis delivered to the heart via a medical lead adapted to be attached witha distal end to tissue of the heart, the medical lead including apenetrating electrode arrangement in the distal end for enablingattachment of the lead to tissue and at least two electrodes arranged onthe electrode arrangement being electrically separated from each other,each being connected to the at least one conductor. In FIGS. 4 and 5,two alternative embodiment of the electrode arrangement includingelectrodes are shown. A selection device is controlled to selectivelyactivate at least one of the electrodes. If this method is performed atan implantation, the physician may select a first electrode to beactivated. The electrode may also be selected automatically, forexample, in accordance with a predetermined scheme, which may be thecase if a post-implant optimization procedure is performed. Then, atstep S102, surface ECG signals or IEGM signals corresponding to aphysiological activity of the heart and/or measurement signalscorresponding to the operation of the electrode are obtained. Thesesignals may be obtained for a predetermined number of consecutivecardiac cycles. The obtained signal may also be processed, for example,an average value may be calculated over the measured cardiac cycles.Thereafter, at step S104, at least one selection parameter or pacingmeasure based on an evaluation of the obtained surface ECG signals orIEGM signals and/or the measurement signals is determined.

At an implantation, at least one pacing measure or selection parameteris obtained to determine the function or the efficiency of therespective electrode. This or these pacing measure(-s) or selectionparameters can be determined by a processing circuit of the implantablemedical device based on, for example, measured surface ECG signalsand/or measured stimulation responses (e.g. thresholds and/or sensingvalues), or by a processing circuit of an external programmer deviceconnected to the implantable medical device or the medical lead.According to one embodiment, the surface ECG is obtained and the QRScomplex and T-wave complex is identified in the surface ECG and when HISbundle is reached, the QRS complex and T-wave complex shouldsubstantially correspond to a native QRS complex and a native T-wavecomplex with respect to morphology, including amplitude, configurationand duration being the result from an intrinsic event. This is describedby Deshmukh et al, in Circulation 2000; 101; 869-877. According toanother alternative, the period of time between a stimulation at HISbundle and the subsequent ventricular event (HIS-ventricular interval orH-V-interval) is determined and this period of time is compared with theperiod of time for a native stimulation, i.e. a spontaneous sensed eventat HIS and the sensed ventricular event. When the HIS bundle is reached,the two periods of time should be substantially equal, i.e. the lengthof the respective periods of time should substantially coincide. Thisalternative is also suitable to use during at a follow-up at thehospital when the patient visits his/her physician.

At step S106, the steps S100, S102, and S104 may be repeated for allelectrodes of the electrode arrangement, or for selected electrodes.Subsequently, at step S108, the selection device is controlled toselectively activate the electrode providing the best HIS bundlesimulation based on the at least one selection parameter, as indicatedabove. However, as the skilled person realizes, the embodiment describedwith reference to FIG. 8 is only exemplifying and there is a number ofconceivable alternative methods. For example, one electrode at a timecan be used and evaluated and when the selection parameter(-s)predetermined conditions with regard to, for example, conduction timefrom HIS bundle to ventricular activation are satisfied, the procedureis stopped and the electrode providing the satisfying result is selectedfor stimulation.

If this method is performed in the chronic state, i.e.post-implantation, the morphology and/or H-V-interval from sensed nativeevents at the bundle of HIS and subsequent sensed ventricular activationobtained from the IEGM (intracardiac electrogram) can be compared with apredetermined reference morphology and/or predetermined referenceH-V-interval. The reference morphology and reference H-V interval arepreferably obtained from the same patient, i.e. the morphology and/orH-V-interval from sensed native events at the bundle of HIS andsubsequent sensed ventricular activation are recorded. A deviation fromthe predetermined reference morphology and/or predetermined referenceH-V-interval may be used as trigger for an automatic test procedure foridentifying a more suitable electrode. In another embodiment forpost-implant optimization, the morphology and/or H-V-interval fromstimulated events at the bundle of HIS and subsequent sensed ventricularactivation obtained from the IEGM (intracardiac electrogram) can becompared with a predetermined reference morphology and/or predeterminedreference H-V-interval. The reference morphology and reference H-Vinterval are preferably obtained from the same patient, i.e. themorphology and/or H-V-interval from stimulated events at the bundle ofHIS and subsequent sensed ventricular activation are recorded. Adeviation from the predetermined reference morphology and/orpredetermined reference H-V-interval may be used as trigger for anautomatic test procedure for identifying a more suitable electrode.

Although an exemplary embodiment of the present invention has been shownand described, it will be apparent to those having ordinary skill in theart that a number of changes, modifications, or alterations to theinventions as described herein may be made. Thus, it is to be understoodthat the above description of the invention and the accompanyingdrawings is to be regarded as a non-limiting example thereof and thatthe scope of protection is defined by the appended patent claims.

We claim as our invention:
 1. A medical system for delivering pacingpulses to HIS bundle of a heart of a patient when implanted in saidpatient, said system comprising: a medical lead, which is adapted to befixated to tissue of said heart, said medical lead including a lead bodyincluding a flexible insulating tubing and at least one conductorarranged within said tubing; a penetrating electrode arrangement coupledto a distal end of the medical lead, the penetrating electrodearrangement including a fixation apparatus adapted to fixate the lead tothe tissue of said heart; and at least two electrodes arranged on saidfixation apparatus, wherein the at least two electrodes are electricallyseparated from each other and wherein the at least two electrodes areelectrically coupled to said at least one conductor; and a selectiondevice connected to the at least two electrodes and being adapted toselectively activate at least one of said electrodes, and an implantablemedical device configured to be coupled to said medical lead, saidmedical device comprising a pacing circuit adapted to deliver saidpacing pulses to said heart via said selection device and said medicallead.
 2. The medical system according to claim 1, wherein said systemfurther comprises an extracorporeal programmer device being adapted tocontrol said selection device.
 3. The medical system according to claim2, wherein said programmer device further comprises a processing deviceconfigured to control said selection device to selectively activate atleast one of said electrodes to direct said pacing pulses to HIS bundle,said processing device is adapted to control said selection device toselectively activate at least one of said electrodes by connecting saidat least one electrode with said pacing circuit based on at least oneselection parameter.
 4. The medical system according to claim 3, whereinsaid programmer device further is configured to obtain ECG or IEGMsignals corresponding to a physiological activity of said heart and/ormeasurement signals corresponding to the operation of said electrodesfrom said measurement circuit.
 5. The medical system according to claim4, wherein said processing device is adapted to determine said at leastone selection parameter based on an evaluation of said obtained ECG,said IEGM signals and/or said measurement signals.
 6. The medical systemaccording to claim 1, wherein said medical device further comprises aprocessing device adapted to control said selection device toselectively activate at least one of said electrodes to direct saidpacing pulses to the HIS bundle, said processing device being configuredto control said selection device to selectively activate at least one ofsaid electrodes by connecting said at least one electrode with saidpacing circuit based on at least one selection parameter.
 7. The medicalsystem according to claim 6, wherein said processing circuit is adaptedto instruct said selection circuit, during a test procedure, to activatesaid electrodes according to a predetermined scheme, evaluate selectionparameters obtained during a pacing period for each respective electrodeto determine which electrode to use for HIS bundle pacing, and instructsaid selection circuit to activate said determined electrode for HISbundle pacing.
 8. The medical system according to claim 1, wherein saidimplantable medical device further comprises a measurement circuitadapted to obtain IEGM signals corresponding to a physiological activityof said heart and/or measurement signals corresponding to the operationof said electrodes.
 9. The medical device according to claim 8, whereinsaid processing circuit is configured to determine a conduction timefrom a sensed native HIS bundle event or from a delivery of at least onepacing pulse to His bundle to a subsequent ventricular activation usingsaid IEGM signals; and instruct said selection circuit to initiate saidtest procedure if said determined conduction time exceeds apredetermined reference threshold.
 10. The medical system according toclaim 8 wherein said measurement circuit is adapted to determine amorphology of a QRS complex for respective consecutive cardiac eventsusing said IEGM signals, and wherein said processing circuit isconfigured to evaluate said determined QRS complex to determine whetherit satisfies predetermined conditions; and instruct said selectioncircuit to initiate a test procedure if said determined QRS complex donot satisfies said predetermined conditions.
 11. The medical systemaccording to claim 1, wherein said selection device is arranged in saidmedical device, or wherein said selection device is arranged in saidmedical lead.
 12. The medical system according to claim 1, wherein saidfixation apparatus includes a rotatable helix adapted for enabling anattachment of the lead to tissue by screwing the helix into the tissue,said helix comprising said at least two electrodes or wherein saidfixation apparatus includes a rotatable helix adapted for enabling anattachment of the lead to tissue by screwing the helix into the tissueand an penetrating pin comprising said at least two electrodes, saidpenetrating pin being arranged such that said helix partly encirclessaid pin.
 13. A method for delivering pacing pulses to the HIS bundle ofa heart of a patient, said method comprising: delivering pacing pulsesto said heart via a medical lead, the medical lead being adapted to befixated to tissue of said heart, said medical lead including a lead bodyincluding a flexible insulating tubing and at least one conductorarranged within said tubing; a penetrating electrode arrangement coupledto the distal end of the lead, the penetrating electrode arrangementincluding a fixation apparatus for enabling fixation of the lead totissue; and at least two electrodes arranged on said fixation apparatus,wherein the at least two electrodes are electrically separated from eachother and wherein the at least two electrodes are each electricallycoupled to said at least one conductor; and controlling a selectiondevice to selectively activate at least one of said electrodes to directpacing pulses to HIS bundle.
 14. The method according to claim 13,wherein said step of controlling comprises controlling said selectiondevice to selectively activate at least one of said electrodes based onat least one selection parameter.
 15. The method according to claim 13,further comprising the steps of: obtaining surface ECG or IEGM signalscorresponding to a physiological activity of said heart and/ormeasurement signals corresponding to the operation of said electrodes,and determining said at least one selection parameter based on anevaluation of said obtained surface ECG or IEGM signals and/or saidmeasurement signals.
 16. The method according to claim 13, furthercomprising the steps of: instructing said selection circuit, during atest procedure, to activate said electrodes according to a predeterminedscheme, evaluating selection parameters obtained during a pacing periodfor each respective electrode to determine which electrode to use forHIS bundle pacing, and instructing said selection circuit to activatesaid determined electrode for HIS bundle pacing.
 17. The methodaccording to claim 16, further comprising the steps of: determining aconduction time from a sensed HIS bundle event or from delivery of atleast one pacing pulse to His bundle to a ventricular activation usingsaid surface ECG or said IEGM signals, and instructing said selectioncircuit to initiate said test procedure if said determined conductiontime exceeds a predetermined reference threshold.
 18. The methodaccording to claim 17 comprising: determining a morphology of a QRScomplex for respective consecutive cardiac events using said surface ECGor said IEGM signals, evaluating said determined QRS complex todetermine whether it satisfies predetermined conditions; and instructingsaid selection circuit to initiate said test procedure if saiddetermined QRS complex do not satisfies said predetermined conditions.19. An implantable medical system for delivering pacing pulses to theHIS bundle of a heart of a patient when implanted in said patient, saidimplantable medical system comprising: an implantable medical devicecomprising a pacing circuit adapted to produce said pacing pulses; anmedical lead being adapted to be fixated to tissue of said heart andincluding a lead body including a flexible insulating tubing and atleast one conductor arranged within said tubing; a penetrating electrodearrangement coupled to a distal end of the conductor, the penetratingelectrode arrangement comprising a rotatable helix adapted for enablingfixation of the lead to tissue by screwing the helix into the tissue,said helix comprising; at least two electrodes arranged on said helix,wherein the at least two electrodes are electrically separated from eachother, and wherein said at least two electrodes can be selectivelyactivated to direct said pacing pulses to HIS bundle.
 20. The medicallead according to claim 19, further comprising a selection deviceconnected between a pacing circuit of said implantable medical deviceand said electrodes, said selection device being adapted to selectivelyactivate at least one of said electrodes.
 21. The medical lead accordingto claim 20, wherein said penetrating electrode arrangement includes arotatable helix adapted for enabling an attachment of the lead to tissueby screwing the helix into the tissue, said helix comprising said atleast two electrodes or wherein said penetrating electrode arrangementincludes a rotatable helix adapted for enabling an attachment of thelead to tissue by screwing the helix into the tissue and an penetratingpin comprising said at least two electrodes, said penetrating pin beingarranged such that said helix partly encircles said pin.
 22. A medicalsystem for delivering pacing pulses to HIS bundle of a heart of apatient when implanted in said patient, the system comprising: a medicallead comprising a lead body including a flexible insulating tubing andat least one conductor arranged within the tubing and a penetratingelectrode arrangement coupled to a distal end of the medical lead, thepenetrating electrode arrangement comprising a rotatable helix adaptedto fixate the lead to tissue by screwing the helix into the tissue and apenetrating pin being arranged such that said helix partly encirclessaid pin and at least two electrodes arranged on the penetratingelectrode arrangement, wherein the at least two electrodes areelectrically separated from each other and wherein the at least twoelectrodes can be selectively activated to direct the pacing pulses toHIS bundle; and an implantable medical device configured to be coupledto the medical lead, the medical device including a pacing circuitadapted to deliver pacing pulses to the heart.